Abstract: A file security system uses a security class set by an access control module. The file security system includes a disk, a kernel memory and an encryption file system. The disk includes a key file in which an encryption key corresponding to the security class is stored and a file encoded by the encryption key. The encryption key stored in the disk is loaded into the kernel memory when the file security system starts operating. The encryption file system extracts an encryption key corresponding to a security class of a file that a user intends to read or store; decodes or encodes the file by using the extracted encryption key; and then provides the decoded file to the user or stores the encoded file in the disk.

Abstract: Disclosed herein is a method of providing a trusted path between a client and a system using an access control processing technique. The method of providing a trusted path between a client and a system includes the step of determining whether access to resources of the system will be permitted or refused on the basis of access control rules and databased attributes set by a security administrator. Thereafter, the client is notified of permission for or refusal of the access in accordance with the result of the determination.

Abstract: A method for interfacing between a transmitter and receiver of a digital broadcasting system using a satellite, includes the steps of: searching a program association table of the receiver for a corresponding program, and detecting a receiver control message packet number; detecting a receiver control message through the detected packet number; detecting public switched telephone network and public switched data network numbers through the receiver control message; searching for a network information table of the receiver and then detecting an event information table packet number at a time zone corresponding to an event information table construction descriptor, in order to search for a corresponding event information table; inserting a VCR reserved recording descriptor into the event information table to impose an identification number on a corresponding program, thereby performing a reserved recording; inserting a price information descriptor table into the event information table to transmit program price